1. Field of the Invention
This invention pertains to decreasing flow around a probe, cannula, needle or trocar, such as during aspiration and irrigation of fluids within a closed volume for medical purposes. More particularly, apparatus and method are provided for minimizing or eliminating fluid flow around a phacoemulsification probe or other instrument during irrigation and aspiration of the eye or human organs or cavities.
2. Description of Related Art
Traditional small incision cataract surgery uses a coaxial irrigation-aspiration system and ultrasound to fragment the cataract material. Recently, Micro-Incision Cataract Surgery (MICS) has evolved, which uses two very small incisions and divides the irrigation mode from the ultrasound-aspiration mode of the phacoemulsification technique, thus introducing “bimanual” phacoemulsification. The advantage of MICS is smaller incisions in the eye, which are less invasive, allow quicker healing and typically leave less astigmatism. In the bi-manual technique the surgeon uses both hands during the phacoemulsification procedure, with separate irrigation and aspiration instruments.
New ultrasound and other fragmenting machines have also increased the appeal of MICS and allowed smaller, tighter incisions with less chance of “wound burn” by reducing the amount of energy employed inside the eye, using techniques such as described in US 2004/0068300, for example. Similarly, vitreous resection has also progressed by the utilization of smaller incisions and bi-manual removal of vitreous. The small vitrectomy tip normally involves use of a hollow shaft enclosing a rotating or isolating blade to which an aspiration line is affixed.
In both instances, cataract lens or vitreous removal, the infusion needle and the mechanically active aspirator needle used in the bi-manual technique are preferably “water tight” in the incision of the eye, so as to form a closed fluid system. Working in a closed environment provides a significant improvement from routine cataract surgery, where the closed chamber concept is not available. There is a need to optimize the probes to allow the balance between outflow and inflow in this new environment. The goal is to have a pressurized volume of fluid in the anterior chamber, posterior chamber or vitreous body of an eye and to minimize the outflow and inflow volumes. The decrease in flow rate into and out of the eye can reduce the circulation inside the eye and lead to greater safety and control of the surgery.
New micro instruments have been designed to be incorporated into the system used by the surgeon in MICS. The new probes may be of smaller size and are designed to be used without an irrigation sleeve. They should be designed to be manipulated efficiently through the micro-incisions without creating enough tension in the corneal tissue to tear the incision or damage the tissue. Friction between the probe and the corneal tissue should preferably be minimized.
It is important to avoid thermal burn when using MICS. Some prior methods depended on cooling the phaco tip and incision tissue by leaking solution through the incision. Newer methods reduce tip temperature by operating in a pulse mode or computer-controlled mode as described in US 2004/0068300, which minimizes the amount of energy input to the ultrasound probe and lowers its temperature, which may decrease the need for leaking through the incision. A Teflon coated tip has also been used in the past, which provides lower friction between the probe and the tissue and adds a thermal insulation layer to the probe.
What is needed is apparatus and method to increase resistance to fluid flow or to provide a limited seal around a phacoemulsification probe or other needle, cannula or trocar through an incision to minimize or prevent fluid leakage or to afford a closed system at normal pressures for performing surgery. The apparatus should also assist in avoiding thermal damage to tissue.